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Dear all,

I am interested to calculate the exciton binding energy of some different structures (nano and bulk).
My question is that, is it reasonable to ignore the e-h coupling and use BSEmod=resonant or causal for this purpose?
If we ignore the e-h coupling so what is the source of exciton binding energy?

I really appreciate your help in advance.

Dear nrbsh,
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About the e-h coupling: there is not a straightforward reason for that. Ignoring the coupling, which is called Tamm-Dancoff approximation, usually it is ok
for bulk and extended structure while it is not a good approximation for finite systems (molecules). Anyway this is something that has to be checked.
Best,
Daniele